#include <fstream>
#include <vector>
using namespace std;

ifstream f("ciur.in");
ofstream g("ciur.out");

int main()
{
    int n,i,s=0;
    vector <int>v(2000001,0);
    f>>n;
    for(int i=3;i<=n;i+=2)
        for(int j=3*i;j<=n;j+=2*i)
        {
            v[j]=1;
        }
    for(int i=3;i<=n;i+=2)
        if(v[i]==0)
        s++;
    g<<s+1;


    f.close();
    g.close();
}